Basically, you apply a matching random "value" to each face you want to phong shade. Then when arghrad does the lighting pass, it pretends the surfaces you selected are curved, and changes the lightmap appropriately. r_speeds are not affected. Compile time may increase slightly. A good way to see the difference is to make a map with two barrels, both 8 sides, one where all the side faces have the value "0" in the surface properties window, and one where they all have the value "531" or whatever.